The present invention relates to the use of hydrazone derivatives in combination with copper for controlling algae. In particular, the present invention relates to a method for controlling algae by the use of certain hydrazone derivatives when applied in synergistic mixtures with copper. Such mixtures of hydrazone derivatives with copper are known to exert a synergistic effect towards fungi. Examples include those disclosed in PCT Patent Application PCT/US10/021,040, filed on 14 Jan. 2010.
The presence of algae and other fouling organisms in various aqueous systems or systems exposed to water such as lattices, paints, coatings, cooling water systems, the marine environment, and decorative ponds can cause deterioration or disfigurement of the system. For example, painted surfaces may be disfigured by the unsightly buildup of algae, detracting from the overall aesthetics of the painted article and cooling towers or boats may lose efficiency due to the buildup of algae on surfaces. It is conventional to practice methods which inhibit the algal deterioration of such systems by incorporating a variety of additives or combinations of additives that are characterized by having antialgal activity.
A wide variety of materials have been used to control algae in different environments, including; chlorine/bromine compounds, glutaraldehyde, isothiazoles, organotin formulations, copper salts, quaternary ammonium compounds and triazines. However, each of these materials has deficiencies related to toxicity, pH and temperature sensitivity, limited effectiveness, chemical stability, and/or compatibility. Due to these deficiencies in conventional antialgal compounds, there is a continuing need for more effective antialgal agents.
Copper and copper products are widely used as aquatic biocides and antifouling agents in fresh or marine environments to control unwanted organisms based on the toxicity of copper towards algae, fungi, macrophytes and mollusks (Handbook of Copper Compounds and Applications, edited by H. W. Richardson and published by Marcel Dekker, Inc. New York (1997), which is expressly incorporated by reference herein).
Ecological risk assessment studies have shown that copper products, which normally are applied at high use rates, may be toxic to birds, mammals, fish and other aquatic species (“Reregistration Eligibility Decision (RED) for Coppers,” EPA 738-R-06-020, July 2006, which is expressly incorporated by reference herein). Thus, while copper is a highly useful agent for controlling the growth of undesirable organisms in different environments, it is desirable to minimize the amount of copper applied.
We have discovered that hydrazone derivatives in combination with copper inhibit the growth of algae. Due to strong synergism between hydrazones and copper, the amount of copper traditionally needed to inhibit growth of algae can be greatly reduced in the presence of hydrazone derivatives. The present invention is a method for controlling algae, comprising applying to the locus of the algae an algicidally effective amount of one or more compounds of the structural formula I in combination with copper.